Replace Google Site Search

This is about a website comprising of a Joomla and two Mediawiki components. Joomla contains the welcome page and links to the two Wikis. The two Wiki components reside in two foreign subfolders in the Joomla file system. One of the Wikis is a bit heavy. Its archive is almost 3 Gigabytes. Until recently the global search, yielding results from both Joomla and Wiki pages, was handled by a Google Site Search paid subscription and the “googleSearch (CSE)” Joomla module. Since Google seems to be ending this service, the new site search results include advertising and the indexing seems to have gotten lazy. I'd like to find a way to restore the initial functionality offered by the Google paid service. The main requirements are: [ ] the search box should appear in Joomla [ ] the search should be able to correct both English and German spelling mistakes, just like Google Site Search [ ] the search results should include some non-Joomla URLs on the same domain (derived from the two Wiki folders in the Joomla file system) [ ] the search results should not include content from foreign websites (such as advertising) [ ] the search should be as fast as the one offered by Google Site Search / Google Custom Search [ ] if it uses a third party service (like Cludo, for example), it should not cost more than $200 a year. I'd prefer a self-hosted solution (for example with a Joomla extension or Solr or Elastic or whatever works). Everything is hosted on a dedicated Ubuntu 16 server. Joomla gets updated regularly. I am aware of the Joomla search extensions, but I do not know if they fulfill my requirements, nor do I know which extension is the right one. I also heard that the native Joomla Smart Search is not so smart. I essentially need you to tell me how to do this, after which I'll attempt to do it myself. Of course, if I get stuck, I'll ask for your help, which would come with additional fees on Freelancer. Thank you.